ETH study reveals decreasing material diversity in nano environmental behaviour research
Nanoparticles behave in an extremely complex manner in the environment. In a large overview study, environmental scientists at the ETH in Switzerland have shown that currently there is a lack of systematic experimental data that could help in understanding the nanoparticles in a comprehensive way.
The nanotechnology industry is flourishing. Several thousands of tonnes of man-made nanoparticles are globally produced every year; sooner or later, a particular part of them will end up in bodies of soil or water. However, even experts have difficulty in explaining what exactly happens to the nanoparticles there. The question is indeed complex, because there are a variety of man-made (engineered) nanoparticles, and also because the particles behave differently in the environment based on the prevailing conditions.
Researchers, headed by Martin Scheringer, aimed at bringing about some clarity to this issue. These researchers reviewed 270 scientific studies, including almost 1,000 laboratory experiments described in these studies, in order to search for patterns in the behaviour of engineered nanoparticles. The team aimed at making universal predictions about the behaviour of the particles.
Particles attach themselves to everything
However, an extremely mixed picture was discovered by the researchers when they looked at the data. “The situation is more complex than many scientists would previously have predicted,” says Scheringer. “We need to recognise that we can’t draw a uniform picture with the data available to us today.”
Nicole Sani-Kast, a doctoral student in Scheringer’s group and first author of the analysis featured in the journal PNAS, adds: “Engineered nanoparticles behave very dynamically and are highly reactive. They attach themselves to everything they find: to other nanoparticles in order to form agglomerates, or to other molecules present in the environment.”
The speed at which the particles react and to what exactly they react depends on a wide range of factors such as the acidity of the soil or water, the concentration of the existing salts and minerals, and most of all, the composition of the organic substances present in the soil or dissolved in the water. What makes things a lot more complicated refers to the fact that the engineered nanoparticles frequently have a surface coating. Based on the environmental conditions, the particles lose or retain their coating, thus influencing their reaction behaviour.
Sani-Kast evaluated the results available in the literature by using a network analysis for the very first time in this research. This technique, mostly used in social research for measuring networks of social relations, allowed Sani-Kast to demonstrate that the data available on engineered nanoparticles is poorly structured, insufficiently diverse and inconsistent.
More methods for machine learning
“If more structured, consistent and sufficiently diverse data were available, it may be possible to discover universal patterns using machine learning methods,” says Scheringer, “but we’re not there yet.” Adequately structured experimental data must first be available.
“In order for the scientific community to carry out such experiments in a systematic and standardised manner, some kind of coordination is necessary,” adds Sani-Kast, but she is aware that coordinating such work is difficult.